It's important to note that most images are not digitized, so if you're looking for something unique you may have better luck scanning it from a book. There many types of scanners available throughout the Library. The flatbed scanners are most appropriate for digitizing images.
If you'd like to present your image in a PowerPoint, it should be at least 72ppi, and about 1024x768 pixels. If you'd like to publish or print the image, it should be at least 300dpi and about 1,500x900 pixels. Please check copyright restrictions and publisher guidelines.
In the details section of a catalog record, the format field will tell you if a book has illustrations.

Below are a few examples that will help you find images:
Many indexes and journals that the library subscribes to allow users to search specifically for pages containing images. Simply look for "page image" in the filter options, or "captions" or "illustration" in drop down menus. Below are a few examples:
Provides page images of back issues of the core scholarly journals in the humanities, social sciences, and basic sciences from the earliest issues to within a few years of current publication. Users may browse by journal title or discipline, or may search the full-text or citations/abstracts. New issues of existing titles and new titles are added approximately on a weekly basis. The University of Illinois has access to the following JSTOR collections: Arts & Sciences I-XV, 19th Century British Pamphlets, Business IV, Global Plants, Hebrew Journals, Ireland, Life Sciences Collection, Lives of Literature, Security Studies, Struggles for Freedom - South Africa, Sustainability, and World Heritage Sites - Africa.